database security for storing online credit card information

I'm gathering some requirements for a new database that will serve for a .NET website that will accept online credit card applications for businesses. It has been awhile since I've worked with SQL Server and I'm trying get prepared on the what questions I need to address around designing this database?

There will need to be tables setup that keep track of the credit card approval process (all steps during it's approval).
There will need to be the ability to differentiate between new account requests and adding a new cardholder to an existing account. A different application will be required for both scenarios.
There will need to be the ability to attach large documents.

So, my first question, is what are the ways to secure the database? I have a concern that if credit card information is going to be stored in a database that it needs to be secure. What are the different options to secure that type of sensitive financial information? What is the best approach?

It also seems that instead of storing large files in the database, that strong links to the files stored on the file system would be better and more secure?

I apologize for the general questions, but I'm just trying to get some guidance on what initial questions I should be thinking about in preparation for the actual design (structure) of the database.

I would think that beyond just the database being secure... you want to add further security such as encrypting the credit card numbers within the database.

That way, even if a hacker got access to the database (such as a SQL injection... which you SHOULD already be protecting yourself from) they still don't have the credit card numbers until they also hack the encryption.

Also you could look at using an API for PCI compliance. It may cost a little bit more, but it could be worth it in the end. Here are a couple that I found, but you should look into them extensively before using any of them,

You have to be as secure as possible to protect yourself and the business as well as the customer information. It may save you a future lawsuit if it gets hacked. PCI compliance is very complicated thing to do correctly. The best way to not get PCI data stolen from your database is to not have it stored in your database.

Most of the time you have to go to a third party company that handles ALL the secure side of the credit cards.
They will give you the encrypting code for you to check the card for all the needs that you need (new account, returning customer, credits, subtactions of active account, etc.).
Then all you have to do is setup a SQL db that will keep track of that customer card activity.
By doing this it will remove you (your company) from the liablity side of credit card transactions.

Thanks for everyone's input. Using a third party company to handle all the security sounds like the safest option. How does that exactly work? For example, do they only maintain the card information and I would store some key in the SQL Database that would return all the credit card information for a specific account? What is involved in linking the SQL Server database to a third party company?

Introduction
In my previous article (http://www.experts-exchange.com/Microsoft/Development/MS-SQL-Server/SSIS/A_9150-Loading-XML-Using-SSIS.html) I showed you how the XML Source component can be used to load XML files into a SQL Server database, us…

Familiarize people with the process of retrieving data from SQL Server using an Access pass-thru query. Microsoft Access is a very powerful client/server development tool. One of the ways that you can retrieve data from a SQL Server is by using a pa…